EXPERIMENTAL AND CLINICAL TRANSPLANTATION

Objectives: The common femoral artery is the standard site for immediate vascular access when initiating adult venoarterial extracorporeal membrane oxygenation. However, this approach is fraught with problems such as femoral artery occlusion, distal limb ischemia, reperfusion injury resulting in compartment syndrome, retroperitoneal hemorrhage, thrombosis, embolization, and most importantly, pulmonary edema. Here, we show our preference of using the subclavian artery with a side graft as a different cannulation technique for outflow of extracorporeal membrane oxygenation, which can avoid complications associated with different access techniques.

Materials and Methods: Between September 2013 and December 2014, our group established venoarterial extracorporeal membrane oxygenation via subclavian artery-percutaneous femoral vein cannulation in 11 patients (81.1% men). Mean age was 33 ± 11.1 years (range, 16-55 y).

Results: For this technique, the subclavian artery was slung by retrotapes (Retract-o-Tape; Quest Medical Inc. Allen, TX, USA) proximally and distally before arteriotomy. An 8-mm polyethylene terephthalate (Dacron) graft was then sutured in “end-to-side” fashion. The proximal retrotape was removed, and the distal retrotape was passed through a snare. This maneuver allowed us to manage distal flow of subclavian artery by tightening this tape, thus avoiding complications associated with right arm hyperperfusion. After venoarterial extracorporeal membrane oxygenation was established, central venous pressure and lactate levels decreased, and improvements in arterial blood-gas parameters were maintained.

Conclusions: Our protocol for venoarterial extracorporeal membrane oxygenation cannulation uses the subclavian artery for arterial access and provides a safe and perhaps improved means for providing venoarterial extracorporeal membrane oxygenation support.

Key words : Cardiogenic shock, Mechanical circulatory support, Peripheral cannulation

The use of circulatory support devices, such as extracorporeal membrane oxygenation (ECMO), has been increasing in recent years. There are 2 varieties of ECMO application: venoarterial (VA) and venovenous ECMO. Venoarterial ECMO helps to maintain hemodynamic support and to provide adequate tissue oxygenation, enhances coronary blood flow, and reduces restoration time of spontaneous circulation in patients with hemodynamic instability.^1,2 Furthermore, VA-ECMO support could be lifesaving in the setting of cardiopulmonary arrest and refractory cardiogenic shock.¹

The common femoral artery is often used for arterial cannulation because the common femoral artery provides easy access for arterial cannulation. However, this approach is associated with potential complications, including inadequate upper body perfusion, lower extremity ischemia, and insufficient unloading of the left ventricle (LV).^3-5 The failing LV may not have sufficient contractile reserve for aortic valve opening, resulting in elevated LV cavity pressure, pulmonary venous hypertension, pulmonary vascular injury, and acute respiratory distress syndrome.⁶ The ideal approach for arterial cannulation with either central or peripheral support is still controversial.⁷

Here, we describe our preference of using the subclavian artery with a side graft as a different cannulation technique for outflow of ECMO, which can avoid the complications associated with different access techniques.

Materials and Methods

Patient population
Between September 2013 and December 2014, we established VA-ECMO in 11 patients with urgent or emergency conditions. In all patients, subclavian artery cannulation was carried out as an arterial access by the same surgical ECMO team. Indications for VA-ECMO were persistent cardiogenic shock, advanced heart failure, and refractory respiratory failure in the setting of severe pulmonary hypertension with right heart failure. The ECMO circuit consisted of a Medos oxygenator (Medos Medizintechnik, Stolberg, Germany) and a centrifugal pump. The patients were treated with ECMO according to an established low-dose anticoagulation (activated clotting time between 150 and 200 s) and lung-protective ventilation protocol. Positive inotropic drugs and pulmonary vasodilators were administered to decrease pulmonary artery pressure and maintain optimal hemodynamics.

Cannulation technique
Venoarterial ECMO involves a standardized arterial cannulation with variant peripheral venous cannulation techniques. Our protocol for VA-ECMO cannulation uses the subclavian artery for arterial access and femoral vein for venous access. The distal right subclavian artery is exposed through a 3- to 4-cm subclavicular incision. The subclavian artery is slung by retrotapes (Retract-o-Tape; Quest Medical Inc. Allen, TX, USA) proximally and distally before arteriotomy (Figure 1), and then an 8-mm polyethylene terephthalate (Dacron) graft is sutured in an “end-to-side” fashion using 6-0 polypropylene suture (Figure 2). A 21-French (F) cannula (Calmed Labs, Costa Mesa, CA, USA) was inserted into the graft until it advanced up to the arteriotomy. The proximal retrotape was removed; however, the distal retrotape was passed through a snare (Figure 3); this allowed us to manage distal flow of subclavian artery by tightening this tape to avoid complications associated with right arm hyperperfusion.

During cardiopulmonary resuscitation, our preference is to use percutaneous femoral artery cannulation for ECMO. At the end of a successful cardiopulmonary resuscitation, we transport the arterial cannula to the subclavian artery.

The choice for venous access sites and size of the cannula depends on the patient and the clinical scenario. Femoral venous cannulation is usually carried out percutaneously or by cut down. Transthoracic or transesophageal echocardiography is used to ensure that the venous cannulas are positioned just above the inferior vena cava-right atrial junction. We then attach the ECMO circuit to the cannula ports to avoid air entrapment and thus initiate ECMO.

Between September 2013 and December 2014, VA-ECMO was established via subclavian artery-percutaneous femoral vein cannulation in 11 patients (81.1% men). In 2 patients, circulation was administered via percutaneous femoral artery-vein cannulation under cardiopulmonary resuscitation. After hemodynamic parameters were stabilized, femoral artery cannula was transferred to the subclavian artery.

Mean age of patients was 33 ± 11.1 years (range, 16-55 y). Demographic characteristics are summarized in Table 1. Three patients, transferred from other centers, had intra-aortic balloon pumps inserted. We used 24F or larger venous cannulas, especially in patients with a body surface area ≥ 1.7 m2, to ensure sufficient inflow and to avoid hemolysis. In all patients, we selected 21F arterial cannulas. After ECMO was established, central venous pressure and lactate levels decreased; improvements in arterial blood-gas parameters (summarized in Table 2) were indicators for effective perfusion. Preoperative and postoperative end-organ perfusion data of ECMO are summarized in Table 3. In evaluation of early (day 3) postoperative results, lactate and liver enzyme levels had decreased; however, urea and creatinine levels were found to be elevated.

Upper extremity circumferences were continuously measured. None of the patients experienced pulmonary edema or right upper extremity edema due to hyperperfusion. Systolic artery pressure was 81.6 ± 11.6 mm Hg (range, 70-100 mm Hg) on right upper extremity and 73.2 ± 12.6 mm Hg (range, 65-95 mm Hg) on left upper extremity. We did not need to squeeze the distal snare in any of the patients. In 2 patients, the technique was a bridge to orthotopic heart transplant. Another 2 patients with right heart failure due to acute cellular rejection had died. Four other patients died due to infection and multiorgan failure while on wait list for transplant. Three ECMO oxygenators were changed due to oxygenator dysfunction.

Venoarterial ECMO takes deoxygenated blood from a central vein or the right atrium, pumps it past the oxygenator, and then returns the oxygenated blood, under pressure, to the arterial side of the circulation. This form of ECMO partially supports acute cardiopulmonary failure. The femoral artery is the standard site for immediate vascular access when initiating adult VA-ECMO.⁸ Percutaneous implantation is less invasive than the approach used in other short-term devices, with femoral cannulation most commonly used due to its simplicity. In the setting of LV dysfunction, however, one must be wary of the increased afterload of the heart when exposed to retrograde flow of peripheral cannulation. This can lead to increased left ventricular pressure and insufficient blood drainage to unload a failing LV. As a result, the failing LV may not have sufficient contractility to open the aortic valve, resulting in elevated LV cavity pressure, which can also lead to pulmonary venous hypertension, pulmonary vascular injury, pulmonary edema, and acute respiratory distress syndrome, an especially significant concern in patients with severe mitral insufficiency.^6,9,10 Furthermore, inadequate unloading of the LV in association with stasis and in the presence of infarcted myocardium can lead to substantial thrombus formation within the LV cavity.11 The combination of extensive LV and pulmonary vascular thrombosis with acute respiratory distress syndrome would limit options for recovery, heart transplant, or transition to long-term ventricular assist device systems.^12,13

To avoid these complications, the LV requires decompression. Traditional methods for management of LV distension during VA-ECMO include intra-aortic balloon pumps,^14,15 percutaneous atrial septostomy with a catheter placed into the left atrium, and central ECMO cannulation with direct inflow cannula placement into the left atrium or LV.¹⁶ One of the methods of LV unloading is using an Impella Recover LP 2.5 (Abiomed, Danvers, MA, USA) for the purpose of LV decompression.^6,10,11 During VA-ECMO, the intra-aortic balloon pump is often unable to unload adequately the LV with severe dysfunction and is the least effective technique.¹⁷Although a left atrial septostomy will decrease LV distension, flow is diverted away from the LV and therefore does not fully prevent stasis and thrombus formation within the LV cavity.¹¹ Furthermore, during transition to a left ventricular assist device, the atrial septum needs to be repaired. Central ECMO cannulation of the LV is effective, however, and requires sternotomy or thoracotomy for placement. Sibbald and associates reported several complications with the Impella LP 2.5 pump, such as hemolysis, aortic valve insufficiency, and pump thrombosis.¹⁸ Cheng and associates¹¹ reported that lactate dehydrogenase levels were higher after Impella implantation compared with ECMO alone. Percutaneous cannulation of the femoral artery and vein allows for rapid initiation of support; however, the femoral arterial cannula can be partially or totally occlusive, thereby perhaps leading to distal limb ischemia.^3,5 As a result of this ischemia, devastating limb loss may occur. Several techniques have been described to perfuse the ipsilateral lower extremity to decrease the rate of limb ischemia.^19,20 However, it is not known whether there are specific patient or clinical characteristics that increase the risk of or predict the development of limb ischemia. In a series of 569 patients undergoing cardiopulmonary support, femoral artery occlusion related to the cannula was observed in approximately 2% of cases, with femoral vessel morbidity occurring in 11%.²¹ Contemporary studies have suggested that the incidence of vascular complications among ECMO patients is anywhere between 10% and 70%.^21-24 Ganslmeier and associates²⁵ reported a 3.2% rate of limb ischemia, even though distal limb perfusion catheters were implanted only for small femoral vessels as demonstrated by sonography. In patients with severe peripheral vascular disease, these risks are heightened and may be considered a relative contraindication to femoral artery cannulation. To limit vascular limb complications, alternative cannulation sites such as the axillary artery have been considered. However, these cannulation sites are not practical in emergency circumstances as they may interfere with cardiopulmonary resuscitation because they require open surgical access to the vessels.^24,26,27 Moreover, several complications have also been reported, such as thrombosis and brachial plexus traction injury.²⁶ Few reports are available describing the role of the subclavian artery.^4,28 Subclavian artery cannulation is a viable alternative method for preserving cardiac blood flow, while limiting the risks associated with femoral artery cannulation. Other benefits of subclavian artery cannulation include “central” support with antegrade flow while avoiding the need for sternotomy and direct aortic cannulation, which are frequently required for adult central ECMO perfusion.

In our center, use of the distal subclavian artery with an end-to-side graft is the preferred method for VA-ECMO, without the need for median sternotomy or without incurring the complications associated with femoral artery cannulation. Our experience suggests that subclavian artery cannulation can sufficiently decompress the LV. Thus, we experience neither pulmonary edema nor the vascular complications of femoral artery. We prefer to use distal subclavian artery banding to avoid complications associated with right arm hyperperfusion.

In this study, the lactate and liver enzyme levels had decreased; however, urea and creatinine levels were found to be elevated in the early (day 3) postoperative period. Extracorporeal membrane oxygenation support can be easily initiated and allows, in some cases, a rapid recovery of organ function. However, this recovery is usually progressive, and a continuous renal replacement therapy (hemodialysis) may be required.²⁹ Rubin and associates reported that 75% of their patients required temporary hemodialysis or hemofiltration without delay.³⁰

Our opinion is that subclavian artery cannulation provides a safe and perhaps improved means for providing VA-ECMO support. Additional studies will be required to quantify potential benefits seen in these patients compared with those who are bridged to transplant with mechanical circulatory support using more conventional cannulation strategies. Furthermore, in this technique, decannulation is an easy procedure; it consists of ligating the graft either by using a vascular stapler or by oversewing the graft after cannula removal.

Volume: 15 Issue: 6 December 2017

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